Stellar blast gamma ray was aimed at earth: NASA

Washington, Sep 11 (Xinhua) Data from satellites and observatories around the globe show a jet from a powerful stellar explosion witnessed March 19 was aimed almost directly at the Earth, the US space agency NASA has reported.NASA’s Swift satellite detected the explosion - formally named GRB 080319B - and pinpointed its position in the constellation Bootes. The event, called a gamma-ray burst, became bright enough for human eyes to see.

Observations of the event are giving astronomers the most detailed portrait of a burst ever recorded.

At the same moment Swift saw the burst, the Russian KONUS instrument on NASA’s Wind satellite also sensed the gamma rays and provided a wide view of their spectral structure.

A robotic wide-field optical camera called “Pi of the Sky” in Chile simultaneously captured the burst’s first visible light.

Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. The dying star was 7.5 billion light years away.

A light year is the distance light travels in a vacuum at a speed of 300,000 km a second which is roughly equal to 10 trillion kilometres in a year.

In a paper to appear in Thursday’s issue of Nature, Judith Racusin of Pennsylvania State University and a team of 92 co-authors report on observations across the spectrum that began 30 minutes before the explosion and its afterglow that existed for months.

The team concludes the burst’s extraordinary brightness arose from a jet that shot material directly toward the earth at 99.99995 percent the speed of light.

Gamma ray bursts are the universe’s most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star’s core collapses, it creates a black hole or neutron star that drives powerful gas jets outward through processes not fully understood.

These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.